Grinding wheel angle dressers

ABSTRACT

The present invention relates to a device for dressing the peripheral face or faces of abrasive grinding wheels to any desired angle within 180* of arc, and has particular reference to a portable, relatively simple, and compact dressing device which embodies mechanisms whereby the same device is capable of being rapidly and accurately set to either (1) dress the peripheral face or faces of an abrasive grinding wheel to any increment of, say, 15* through 180* of arc by the relatively simple and accurate operation of inserting a selector pin into any chosen one of a predetermined number, say 13 slots or stations, spaced, say 15* apart, or (2) wherein the same device may also be employed in cases where micromatic settings are necessary or required, by the use of gauge blocks or combinations of gauge blocks of a sufficient and predetermined overall length or width which may be readily determined by mathematical calculation of the sine of any degree of angle or component fractions thereof throughout the entire 180* of arc.

secondary coil or coils of said ignition coil or coils; and solidstate-type switch means adapted to be controlled by the output of said signal coil for determining said discharge time points for said capacitor or capacitors; said n being so selected that sparks may be struck from each ignition plug when its associated cylinder is in its predetermined normal ignition position and when the cylinder is in any position on any of its strokes other than the compression stroke.

2. An ignition system as set forth in claim l, in which when said engine is a one-cylinder engine, said n is an integer selected from the group comprising 2, 3 and 4.

3. An ignition system as set forth in claim l, in which when said engine is a two-cylinder engine, said n is an integer selected from the group comprising 2 and 4.

4. An ignition system as set forth in claim l, in which when said engine is a three-cylinder engine, said n is 3.

5. An ignition system as set forth in claim l, in which when said engine is a four-cylinder engine, said n is 4.

6. An ignition system as set forth in claim ll, in which said magnet-type generator houses said capacitor-charging coil and said signal coil in proximity to each other in the interior of said generator.

7. An ignition system as set forth in claim l, in which said magnet-type generator comprises a rotor having 2n poles; and a stator having a lighting coil wound on an iron core, a capacitor-charging coil wound on a second iron core and a signal coil wound on a third iron core; said iron core for the capacitor-charging coil and that for said signal coil being disposed in a spaced one-upon-another relation extending axially of said generator.

8. An ignition system as set forth in claim 7, in which said 2n poles of the rotor comprise 2n magnets disposed in an equally spaced relation along the inner periphery of a cup-shaped flywheel.

9. An ignition system as set forth in claim 7, in which said 2n poles of the rotor comprise n magnets and n iron pieces which are alternately arranged in an equally spaced relation along the inner periphery of a cup-shaped flywheel.

i0. An ignition system as set forth in claim l, in which said switch means is a thyristor.

lll. An ignition system as set forth in claim l, in which the control terminal of said switch means is provided with a means which is adapted to eliminate any abnormal voltage which may be generated in said signal coil.

l2. An ignition system as set forth in claim lll, in which said means for eliminating the abnormal voltage is a Zener diode having an inverse voltage characteristic, said Zener diode being adapted not to break down at said abnormal voltage.

13. An ignition system as set forth in claim ll, in which said means for eliminating the abnormal voltage is a circuit comprising a capacitor and a resistor in parallel connected to each other.

M. An ignition system for a two-cycle engine comprising a magnet-type generator which includes a rotor having a magnetic field provided with 2n poles (n is an integer of two or more), a capacitor-charging coil and a signal coil, said capacitor-charging and signal coils being disposed axially of said generator in a spaced one-uponanother relation; a capacitor or capacitors adapted to be charged with the output of said capacitor-charging coil', an ignition coil or coils having a primary coil or coils through which a discharge current flows when the load on said capacitor or capacitors is discharged at predetermined time points; an ignition plug or plugs connected to the secondary plug or plugs of said ignition coil or coils; a thyristor adapted to be controlled by the output of said signal coil for determining said predetermined discharge time points for said capacitor or capacitors; and means disposed between the gate of said thyristor and said signal coil for eliminating any abnormal voltage to be induced in the signal coil; said n being so selected that sparks are to be struck from each ignition plug when its associated cylinder is in its predetermined normal sparking position and in any position on its strokesother than its com ression stroke.

15. Ari ignition system as set orth in claim M, 1n which said means for eliminating the abnomial voltage is a Zener diode having an inverse voltage characteristic wherein said Zener diode will not break down at said abnormal voltage.

16. Ari ignition system as set forth in claim 14, in which said means for eliminating said abnormal voltage is a circuit comprising a capacitor and a resistor in parallel connected to each other.

i7. An ignition system as set forth in claim Mi, in which when said engine is a one-cylinder engine, said n is an integer selected from the group comprising 2, 3 and 4.

l. Ari ignition system as set forth in claim i4, in which when said engine is a two-cylinder engine, said n is an integer selected from the group comprising 2 and 4.

19. An ignition system as set forth in claim lll, in which when said engine is a three-cylinder engine, said n is 3.

20. An ignition system as set forth in claim l, in which when said engine is a four-cylinder engine, said n is 4.

GRINDING WHEEL ANGLE DRESSERS 1t is an object of the present invention to provide a device for dressing the peripheral face or faces of an abrasive grinding wheel which device is portable and can be readily placed in position with respect to a grinding wheel, which device is compact and relatively simple in construction and operation, and which is highly accurate and eicient in the purposes for which designed.

It is an object of the present invention to provide a device of the type referred to above which is of the more or less conventional diamond nib-type, wherein said diamond nib or nibs are reciprocated back and forth in contact with the peripheral face or faces of the grinding wheel to dress, true or cut said face or faces to the desired angle or angles, and wherein the angularity of the setting of said dressing device is obtained by the insertion of a selector pin within any chosen one of separate and circumferentially spaced notches or stations on a rotatable and adjustable index plate in which said notches or stations are disposed in circumferentially spaced relation at, say, 15 intervals.

It is a further object of the present invention to provide a device of the type referred to above which may be readily set as described in the preceding paragraph to accomplish the results set forth in said paragraph, and in which said device may also be employed in cases where micromatic settings are necessary or required in order to dress the peripheral face or faces of a grinding wheel to various precise angles between the setting of the device in accordance with the selector pin and separate notches or stations referred to in the preceding paragraph, by the use of a gauge block or combinations of gauge blocks of sufficient overall length or width to set the device for dressing the face or faces of the grinding wheel to the desired angle or angles, the required effective overall length or width of which gauge block or blocks being readily determined by the relatively simple step of ascertaining by mathematical calculation the sine of the selected and predetermined angle which may fall within any one of the several spaced 15 increments.

Further objects of the present invention and the means by which said objects are accomplished, will be readily apparent from the following description of the construction and operation of the device presented herein, and from examination of the accompanying drawings wherein, and from examination of the accompanying drawings wherein, for the purpose of illustration there is shown a preferred embodiment thereof, and in which drawings:

FIG. l is a front elevation of a grinding wheel dressing device embodying the features of the present invention and showing a portion of an abrasive wheel positioned in operative relation to said device with said device set to dress one of the peripheral faces of said grinding wheel to a desired angle of 45;

FIG. 2 is a top plan view on a somewhat enlarged scale of the device shown in FIG. l;

FIG. 3 is a fragmentary rear view on a somewhat enlarged scale of the device shown in FIG. l;

FIG. 4 is a side elevational view on a somewhat enlarged scale of the device shown in FIG. l as viewed from the right side of FIG. ll;

FIG. 5 is a fragmentary sectional view on a somewhat enlarged scale of the device shown in FIG. 1 and showing certain details of construction;

FIGS. 6, 7 and I3 are fragmentary views, partly in section of the selector pin and the means for retracting the inner end thereof from or inserting said inner end into one of the circumferentially spaced notches or stations of the rotatable and adjustable index disc;

FIG. is a fragmentary front elevational view of the rotatable and adjustable index disc showing a plurality of notches or stations spaced circumferentially apart and into any one of which notches or stations the inner end of the selector pin may be inserted to obtain the desired angular setting of the device to dress the peripheral face or faces of an abrasive grinding wheel at an angle of 15, 30 or 45;

FIG. 9 is a fragmentary elevational view showing a portion of the index disc recess into which the rotatable and adjustable index disc is disposed, and showing the inner end of the selector pin which enters any one of the circumferentially spaced notches or stations on the index disc shown in FIG. 8;

FIG. l0 is a transverse sectional view on the line 10-10 of FIG. 5 showing the inner end of the binding nut which, when moved inwardly serves to secure the device in its fixed angular position;

FIG. ll is an enlarged fragmentary plan view partly in section showing a portion of the operating handle which, when moved back and forth effects reciprocation of the diamond nib across the peripheral face or faces of the grinding wheel, this figure showing means whereby the angularity of said operating handle with respect to the shaft upon which it is mounted and which it rotates may be changed; and

FIG. l2 is a fragmentary plan view showing the device when it is set to operate the diamond nibs for dressing a peripheral face or faces of a grinding wheel to an angle of 22 and 30 minutes by the use of suitable gauge blocks.

Referring in greater detail to the construction of the mechanisms shown in FIGS. l to 12 of the accompanying drawings wherein like reference numerals are used to designate like parts throughout the several views, the numeral 1 designates the flat metallic surface of a workbench or machine table above which is positioned the abrasive grinding wheel 2 whose peripheral surface is 'to be dressed to the desired angle or angles, which grinding wheel 2 is mounted on and rigidly secured to a shaft 3 rotated by a motor (not shown) of any preferred or conventional-type. The grinding wheel and its drive mechanism includes means by which said grinding wheel may be raised and lowered into and out of contact with the diamond nibs of the dressing device.

The preferred form of the device of the present invention consists of a metallic base portion 4 of substantially rectangular form which is magnetized 'to cooperate with the metallic surface l whereby said device may be moved to the proper position with respect to the grinding wheel 2 and be retained in said position during the dressing operation. Extending upwardly from the base portion t is a vertical riser portion 5 terminating in an upper semicircular top portion 6, said riser portion 5 being provided at its opposite sides near the lower portion thereof with gauge block stops 7. The rear face of said riser portion S is, as best shown in FIGS. 5 and 6 provided with a circular recess 8 hereinafter referred to as the index disc recess, and that portion of the rear face of said riser portion 5 which extends from the wall defining the index disc recess and the outer edge of the top semicircular portion 6 of the rear face of the vertical riser 5 is graduated or calibrated in increments of 15, a zero 9 occupying a position corresponding to l2 o'clock on the dial of a clock, with a second zero 10 occupying a position corresponding to 3 oclock, and with a third zero 11 occupying a position corresponding to 9 oclock. Starting at zero 9 and proceeding in a clockwise direction, numerals l5, 30 and 45 are applied being spaced apart circumferentially at 15 intervals. Starting at zero l0 and proceeding in a counterclockwise direction the numerals 15 and 3l) are applied also spaced apart circumferentially at 15 intervals, the last-mentioned number 30 being spaced apart 15 from the previously-applied numeral 45 on that side of the scale. Starting at zero 9 and proceeding in a counterclockwise direction, numerals 15, 30 and 45 are applied being spaced apart circumferentially at 15 intervals, and starting at zero l1 and proceeding in a clockwise direction, numerals l5 and 30 are applied also spaced apart circumferentially at 15 intervals, the lastmentioned numeral 30 being spaced apart 15 from the lastmentioned previously-applied 45 on that side of the scale.

The internal vertical wall l2 which defines the base of the circular index plate recess 8 fonned in the rear face of the riser member 5 is provided with a centrally located aperture 13 through which aperture there extends and is rigidly secured to said riser portion S a central stud M having an externally threaded end l5 to which threaded end there is threadedly engaged a binding nut i6 having a plurality of circumferentially spaced recesses 17 each adapted to receive therein a coiled compression spring i8 the outer ends of which springs 18 bear upon an annular packing ring I9, The inner end of rigidly mounted stud i4 extends into and through said index plate recess 8 and terminates in the plan of the flat rear face of vertical riser 5.

The rigidly secured central stud I4 is provided with an axially-extending centrally located bore 20 through which extends and is rotatably mounted therein a slide bar operating shaft 21, the rear end of which shaft extends rearwardly beyond the rear face of the vertical riser and has keyed or otherwise rigidly secured thereto a spur gear 22 for a purpose to be hereinafter described. The forward end of slide bar operating shaft 2l is reduced in diameter, which reduced diameter portion is threaded as indicated at 23 and receives thereon an actuating lever angle selector nut 24, the inner face of which nut is recessed as indicated by the numeral 25.

The slide bar operating lever 26 is rigidly secured to a bushing 27 recessed at its forward and rearward ends 28 and 29 respectively, the said recessed forward end 28 extending into the recess 25 of nut 24 and having within said recessed front end 28 a coiled compression spring 30 which surrounds said reduced threaded portion 23, the forward end of which spring 34) bears upon the inner wall defining recess 25 in nut 24 and the rear end of which spring 30 bears against the partition wall 3i which separates recesses 28 and 29 of bushing 27. The innermost face of bushing 27 extends into a recess formed in the forward end of rigidly secured central stud 14 and said innermost face of said bushing 27 is provided with a plurality of radially-extending, diarnetrically-opposed semicircular grooves 32 (see FIG. li), and said slide bar operating sha 2l is provided with a transversely-extending pin 33 of a length exceeding the diameter of said shaft, the arrangement being such that the opposite extended ends of said pin 33 may be selectively positioned in any one of the pairs of diametrically-opposed, semicircular grooves 32 to detennine the angular relation between said slide bar operating shaft 2i and the slide bar operating lever 26.

Rotatably mounted on the end of rigid stud 14 which extends into and through index disc recess 8, is a circular index disc 34 having on the rear face near the periphery thereof an index mark 35 adapted to be brought into registration with a selected one of the apart graduations on the rear, upper portion of vertical riser 5, said index disc 34 also having an outwardly-projecting sine button 36 located at a position diametrically opposite said index mark 35. As shown in plan in FIG. 3 and in side elevation in FIGS. 5 and 6, the front face of said index disc 34 is provided with a plurality of at least 13 radially-disposed notches or stations machined into said front face near the periphery of said disc and spaced circumferentially at l5 intervals, each of said notches or stations being defined by inwardly tapering sidewalls.

The slide bar housing 37 is rigidly secured to the rear surface of said index plate 34 by bolts 33 and 39 and, hence, is rotatable with said index plate, said slide bar housing 37 comprising an elongated bar of substantially rectangular transverse cross section provided along the full length of the upper surface thereof with an open-ended slot defined by inwardly and downwardly inclined, opposed flat walls or surfaces 40 and 4i which provide an elongated slot of V- shaped transverse cross section, which V-shaped slot is closed along the top thereof by a suitable coverplate 42 secured to the upper surface of said slide bar housing 37 by means of stud bolts 43 threadedly engaged within threaded openings in the upper surface of said slide bar housing 37 positioned in axially spaced relation along opposite sides of said V-shaped slot. About midway of the length of said slide bar housing 37, the front face thereof is cutaway transversely of the bottom surface thereof to provide an inwardly-extending passageway for the inner portion of the slide bar operating shaft 2l, and said midportion of said housing is also provided with an upwardly-extending opening 44 of substantially semicylindrical configuration opening into and communicating with the base portion of the V-shaped slot defined by said flat walls or surfaces 40 and 4I, in which semicylindrical opening is disposed the upper portion of spur gear 22, all as clearly disclosed in FIG. 5 of the accompanying drawings. If desired, the coverplate 42 may be provided with spaced rubber cushions 45 backed by pressure buttons 46. As a means for preventing the entry of dirt or grit into the space occupied by spur gear 22, there is provided a protective casing or housing 47 of generally semicircular configuration, having its upper edge provided with an outwardly extending flange secured to the underside of the slide bar housing 37 by screws 48, with its lower turned down flange engaging the rear surface of rotatable index disc 34.

The slide bar comprises an elongated member 49 of substantially V-shaped transverse cross section and of a greater length than that of the slide bar housing 37, the angularity of the side portions of said slide bar 49 corresponding to the angularity of the V-shaped passageway provided by the inclined walls or surfaces 40 and 41 which define said V-shaped passageway so that said slide bar 49 is free to travel or slide back and forth within the slide bar housing 37. One or both of the protruding end portions of slide bar 49 is or are provided with diamond nibs or cutting tools 50 adapted for dressing, truing, or cutting the face or faces of an abrasive grinding wheel to the desired angle or angles. The apex of said V-shaped slide bar 49 is provided with a gear rack, the teeth of which correspond to and mesh with the teeth of spur gear 22, said rack being preferably of a length corresponding substantially to the length of the slide bar housing 37, the arrangement being such that clockwise and counterclockwise rotation of said spur gear 22 through shaft 2l effected by clockwise and counterclockwise movement of slide bar operating lever 26 results in reciprocation, back and forth of said slide bar 49 and the diamond nib or nibs 50 or similar cutting or dressing tools 50 mounted near the end or near opposite ends of said slide bar 49.

Mechanisms will now be described by means of which the device of the present invention is set up to dress, true or cut the face or faces of a grinding wheel to any desired precise angle or angles of 0, 15, 30, or 45 by the relatively simple and rapid expedient of entering a selector pin into a selected notch or station on the index disc 34. Referring particularly to the showings of FIGS. 6, 7 and I3 of the accompanying drawings, it will be seen that an opening 51 is provided in the vertical riser 5, which opening extends from the front face of said riser 5 and opens into the index disc recess 8, said opening 5l being located in a position directly opposite each of the series of circumferentially spaced notches or stations on index disc 34, within which opening there is rigidly secured by means of screw 52 a tubular sleeve 53, the forward end of which sleeve is formed with a double ca rn or spiral surface 54. Adapted for axial sliding movement within said tubular sleeve 53 is a selector pin 55 having at its inner or rear end an axiallyprojecting lug 56 of a size and tapered configuration corresponding to any one of the notches or stations formed in the front face of index disc 34, said selector pin 55 being hollow throughout the greater portion of the length thereof and provided at its front open end with an annular flange 57 of slightly greater diameter than the diameter of said selector pin 55, Diametrically opposite, axially-extending, elongated slots 58 and 59 are provided through the wall defining the hollow portion of said selector pin 55 and a transverse pin 60 extends through said slots and is of a diameter slightly less than the width of said slots, the opposite ends of said pin 60 being anchored in diametrically opposed openings formed near the outer end of tubular sleeve 53, whereby said selector pin is free to slide inwardly and outwardly within said tubular sleeve 53, the extent of such movements being limited by engagement of said pin 60 with the walls defining the ends of said slots. A coiled compression spring 6l is positioned within the hollow portion of selector pin 55 between the wall defining the inner closed end of said hollow portion and the transverse pin 60, which spring tends to force said selector pin 55 inwardly to force the axially-extending lug 56 into engagement with a selected one of the notches or stations on the face of index disc 34. Located between the double cam or spiralshaped outer end of stationary sleeve 53 and the inner face of annular flange 57 is a hollow sleeve 62, the inner end of which sleeve is formed with a double cam or spiral surface 63 in engagement and cooperative relation with the forward double cammed or spiralled outer end 54 of stationary tubular sleeve 53. Surrounding said sleeve 62 and rigidly secured thereto is a knurled tubular sleeve 64 the arrangement being such that simultaneous counterclockwise rotation of said sleeves 64 and 62 will, due to the engagement and cooperative action of the abutting cam or spiral surfaces on the outer end of stationary sleeve 53 and on the inner end of sleeve 62, cause the selector pin 55 to be retracted to remove the engagement between the projecting lug S6 on the inner end of selector pin 55 and the notch or station on index disc 34. Clockwise rotation of said sleeves 64 and 62 will permit the spring 6l to position the projecting lug 56 into the selected notch or station on the index disc 34 and will return the cammed spiralled surfaces 54 and 63 into contact.

Having thus described the construction of the grinding wheel angle dresser of the present application when the same 4 is set up for dressing the face or faces of a grinding wheel to a precise angle or angles of 30 or 45 by the simple and rapid insertion of a selector pin into a selected notch or station spaced 15 apart on an index disc, it is believed that the operation of said device for this purpose will be readily apparent to an operator reasonably skilled in the art to which the invention pertains. Suffice it to say that when it is desired to set up or adjust the device for this specific purpose, it is only necessary to release the binding nut 16 and to rotate the knurled sleeve 64 in a counterclockwise direction to retract the lug 56 from engagement with one of the notches or stations of the index disc 34, and to rotate the said disc and the slide bar housing and its associated parts secured to said index disc, to bring the index mark 35 into registry with one of the selected 15, 30, or 45 degree designations on the scale marked on the upper portion of the rear face of vertical riser 5. When this has been accomplished, the said knurled sleeve 64 is rotated in a clockwise direction whereupon the selector pin 55 is forced inwardly by spring 6l to insert the lug 56 into the selected notch or station on said index disc, thus establishing the precise angle at which the slide bar 37 will travel when the slide bar shaft and spur gear 22 are rotated. The binding nut 16 is then turned to force the inner end thereof into firm and intimate contact with the outer surface of the vertical riser 5 to retain the parts in their previouslyadjusted positions. This having been accomplished, level angle selector nut 24 is rotated outwardly along reduced, threaded portion'23 of shaft 2l thus pemtitting bushing 27 and slide bar operating handle 26 to be moved outwardly to disengage the t diametrically disposed pair of semicircular grooves 32 from contact with pin 33, whereupon said slide bar operating lever 26 and the bushing 27 to which it is rigidly secured may be rotated with respect to shaft 21 to bring said lever 26 to a substantially horizontal position, following which said lever angle selector nut 24 is rotated inwardly along the reduced, threaded portion 23 of shaft 21 to bring a pair of the diametn'cally-opposed, semicircular grooves 32 on the inner end of bushing 27 into contact with pin 33 to thus retain said slide bar operating lever 26 in its substantially horizontal position. The device is now set up and adjusted to dress the face of an abrasive grinding wheel to the desired precise angle of 15, 30, or 45, FIG. 1 of the accompanying drawings showing the device set up to dress the peripheral face or portions thereof of a grinding wheel to a precise angle of 45 whereas FIG. 3 shows the device set up to dre the peripheral face or portions thereof of a grinding wheel to a precise angle of 30. Obviously, the same procedure is followed for a setting of 15.

The device set up or adjusted as set forth above is placed upon the metal surface l of a work bench or work table with the slide bar 49 positioned parallel to the axis of the shaft 3 on which grinding wheel 2 is mounted and with the axis of the slide bar operating shaft 2l transverse to the axis of said shaft 3. When the device has been so located, the motor which drives the grinding wheel 2 through shaft 3 is rotated and the said grinding wheel is then gradually lowered into contact with either the uppermost or lowemlost diamond nib or similar cutting tool 50, FIGS. l and 3 of the accompanying drawings showing said grinding wheel 2 in contact with the lowermost of said diamond nibs or similar cutting tools 50. Slide bar operating handle 26 is then moved about its axis, first in a counterclockwise direction and then in a clockwise direction as viewed in FIG. 1, which alternate movements are repeated throughout the entire dressing operation, and which repeated movements cause alternate rotation in a counterclockwise and clockwise direction, respectively, of slide bar operating shaft 2l and of the spur gear 22 mounted thereon. Due to the operative engagement between spur gear 22 and the rack on the lowermost portion of slide bar 49, said slide bar and the diamond nibs 50 mounted thereon move first in one direction and then in the opposite direction, during which repeated reciprocating movements the rotating grinding wheel 2 is gradually lowered into progressive contact with the reciprocating diamond nibs 50 until such time as all or a portion of the peripheral face of said grinding wheel is dressed to the desired precise angle.

In the event that the requirements are such as to necessitate the dressing of an adjacent portion of the peripheral face of grinding wheel 2 to the same precise angle as that previously formed on said peripheral face to provide said grinding wheel with a uniform V-shaped peripheral configuration, the entire dressing device is moved or turned around and is moved to the opposite side of the grinding wheel and a dressing operation is perfonned corresponding to that just described to dress the said adjacent portion of the peripheral face of said grinding wheel to the desired precise angle, thus providing said peripheral face with the desired uniform V-shaped configuration.

As an alternative procedure to that defined in the preceding paragraph, the entire dressing device may be moved to the opposite side of the grinding wheel 2 without turning the device around 180, and be positioned with the axis of slide bar 49 parallel to the axis of shaft 3 and with the axis of the slide bar operating shaft 21 transverse to the axis of said shaft 3. When thus positioned, binding nut 16 is loosened, selector pin 55 is moved to withdraw lug 56 from engagement with the previously-selected notch or station on index disc 34, and said disc and all mechanisms mounted thereon is rotated in a counterclockwise direction as viewed in FIG. I and past the 0 designation 9, to bring the index mark 35 into registry with one of the desired 15, 30 or 45 designations on that side of the scale marked on the upper portion of the rear face of vertical riser 5. The knurled sleeve 64 is rotated in a clockwise direction whereupon the selector pin 55 is forced inwardly by spring 61 to insert the lug 56 into the selected notch or station on said index disc, The binding nut 16 is then turned to force the inner end thereof into firm and intimate contact with the outer surface of the vertical riser 5 to retain the parts in their adjusted position. The dressing device is then moved into position beneath the grinding wheel 2, and the dressing operation is accomplished in the manner and by the means fully described above.

It will be readily apparent to one skilled in the art to which the present invention relates, that by the use of the present invention, the entire peripheral face of a grinding wheel may be dressed to a perfectly fIat surface, or to a surface of 15, 30 or 45, or that adjacent portions of the said peripheral face may be dressed to the same or different precise angles of 15 increments by the relatively simple, accurate and reliable operation of inserting a selector pin into a desired notch or station in a rotatable index disc, which mechanism accomplishes one of the important features and objects of the present invention. lt will also be apparent that the scale arrangement applied to the rear face of vertical riser and the corresponding arrangement of notches or stations on index disc 34 may be set up for increments of, for example, 5, the number of such angle designations being limited only by the number of notches or stations which may be found on the front face of rotatable index disc 34.

It is an important feature of the present invention that the same dressing device referred to above and operating in the manner and by the means full)I described above, may also be employed to dress the peripheral face or adjacent peripheral portions of said face to precise angles which fall between the angle designations on the scale provided on the rear face of riser 5 and the corresponding notches or stations on rotatable index disc 34. Since the dressing device above described and which operates on the selector pin and rotatable index disc principle cannot be adjusted to dress a grinding wheel to intermediate fractional angles which fall between the incremental angle designations on the aforesaid scale, the means by which the present device may be readily and accurately adjusted and used for this purpose will now be described. As illustrative of the procedure and means by which this result may be accomplished, let it be assumed, for example, that to perfonn the work required by the grinding wheel, it is necessary that the peripheral face or one or both portions thereof be dressed to a precise angle of 22 30 minutes. When a precise angle is required which falls between the incremental angle designations referred to above, resort is had to momentary mathematical calculations to provide the factor of a gauge block or a combination of gauge blocks of a sufficient andpredetermined overall length or width calculated by the sine of any degree of angle or component fractions thereof throughout 180 of arc.

In the dressing device illustrated in the accompanying drawings, it will be noted that the legend 1.550 is applied to the rear face of base portion, this legend indicating the exact distance in inches between either one of gauge block stops 7 and sine button 36 when index mark 35 is in registration with zero mark 9 and the slide bar housing 37 is in a truly horizontal position. To dress the peripheral face or adjacent portions of said face to an angle of 22 30 minutes, reference is made to any one of the numerous readily available handbooks containing trigonometrical tables or trigonometry factors, such, for example Machinerys Handbook published by Industrial Prem, New York, N.Y., Page 201, th Edition, 1955, Tables of Natural Trigonometry Functions" or to "Trigonometry Tables" published by Illinois Tool Works, Chicago, Illinois, or to any one of numerous publications one of which, at least is usually on hand in the average machine shop, and from which it is readily ascertainable that the sine of 22 30 minutes equals 0.38268. This is the distance of vertical rise a l-inch radius will effect from the horizontal for 22 30 of arc. In the device illustrated in the accompanying drawings, the radial distance from the center of rotatable index 34 to the center of sine button 36 is 1.3 inches and, hence the factor 0.38268 is multiplied by 1.3 which provides the figure 0.497, which figure is then subtracted from 1.550 which, as stated above, is the mated distance to the right or left from the surface of the sine button 36 to the right or left gauge block stops 7 when slide block housing 37 is in a truly horizontal or zero position. When 0.497 is subtracted from 1.550, the result is 1.053. A gauge block of a length of 1.053 or a combination of gauge blocks consisting of one 0.950 and another 0.103 is placed on the upper surface of base 4 and adjacent the righthand gauge block stop 7 as viewed in FIG. l2, the binding nut 16 is loosened from contact with the front face of riser 5, the selector pin 55 is moved forwardly to retract lug 56 from engagement with the notch or station in rotatable index disc 34, and the said index disc is rotated from its horizontal position in a counterclockwise direction as viewed in FIG. 12 until said sine button 36 comes into firm and intimate contact with the combination of 'gauge blocks as clearly shown in FIG.

l2, following which binding nut 16 is rotated to clamp or bind the parts in their adjusted position. The dressing device, thus adjusted, is positioned beneath the grinding wheel to be dressed and is located and is operated in the same manner described above in connection with the dressing of the peripheral face or of adjacent portions thereof to angles of 15, 30, etc.

As a further example of the use of trigonometric tables and sine blocks, let it be assumed that the precise angle of the peripheral face of the grinding wheel or adjacent portions thereof is or are to be dressed to an angle of 37 l5. By referring to any one of a number of readily available trigonometric tables, it is readily determined that the sine for this particular angle is 0.60529, which figure is multiplied by 1.3, the result subtracted from 1.550 and the result of this mathematical calculation determines the gauge block combination to be used to obtain the desired angle of 37 l5, which necessitates the use of a gauge block of 0.787 or a combination of gauge blocks totaling 0.787, for example the combination of gauge blocks of 0.650 and 0.137.

As an alternate procedure in cases where the peripheral face or adjacent portions of said face of the grinding wheel is or are to be dressed to precise angles by the use of gauge blocks, let it be said that the distance 1.3 inches is the exact distance from the lowermost edge of sine button 36 to the underlying top surface of base 4 when the slide bar housing 37 is in a truly vertical position with index mark 35 on rotary index disc 34 in registry with zero designation l1 of the scale on the rear face of riser 5. The block combination having been determined as 1.053 by the mathematical calculation described above, the stack of gauge blocks, i.e. 0.950 plus 1.03, is placed in a vertical position on the upper surface of base 4 in a position beneath sine button 36, and slide bar housing 37 and its associated parts are rotated in a clockwise direction as viewed in FIGS. 3 and l2 until said sine button 36 is brought into firm and intimate contact with the top surface of the uppermost gauge block, thus setting the dressing device to dress at an angle or angles of 22 30, or in the above example when the mathematical calculation called for a gauge block combination to provide a dressing angle of 37 l5, setting the dressing device to dress at an angle or angles of 37, l5, (gauge block or combination totaling 0.787

From the foregoing it will be seen that the construction and operation of the dressing device described and illustrated herein serves as a means for accomplishing the stated objects of the present invention as enumerated in the initial portions of the present specification, in that said invention provides a practical, reliable and efficient means embodying in a single dressing device means for rapidly adjusting the device by a selector pin and index disc mechanisms for dressing the peripheral face or adjacent portions of said face to the most common or popular day-to-day angle or angles, and also provides means the setting of which to the desired angle is readily determined by mathematical calculations for adjusting the device by a sine button and gauge block combination to enable the same to dress a grinding wheel to precise, predetermined, fractional angles.

Having thus described and illustrated the present invention,

Iclaim:

l. A device for dressing the peripheral face or portions of said face of an abrasive grinding wheel to the desired precise angle or angles comprising:

a. a base;

b. a vertical riser extending upwardly from said base and having a circular recess in the rear face thereof, said rear face having thereon a scale of angle designations arranged in preselected angular degree increments and surrounding the wall defining said circular recess, the inner wall defining the base of said recess being provided with a centrally located aperture extending through said wall to the front face of said riser;

c. a rigid stud secured within said centrally located aperture and having its rear end portion extending through said circular recess and terminating in the plane of the rear face of said riser, with the front end portion of said stud extending forwardly of the front face of said riser, said stud having an axially extending, open-ended bore throughout the length thereof;

d. an index disc rotatably mounted in said circular recess on that portion of said rigid stud which extends through said circular recess, said index disc having on its rear face near the periphery thereof an index mark adapted to be brought into registration with any one of the angle designations of the scale ori the rear face of said riser, said index disc having on the front face thereof a series of circumferentially-spaced notches spaced apart at distances corresponding to the angle designations of said scale;

e. a selector pin to be engaged within and retractable from one of the series of notches on said index disc, said pin when engaged within one of said series of notches preventing rotation of said index disc on said rigid stud and when retracted from engagement with one of said notches permitting such rotation;

. a slide bar housing rigidly secured to the rear face of said index disc to be rotatable therewith and provided with an open-ended slot extending axially throughout the length of said housing, the wall defining the bottom of said slot having an opening therein about midway of the length thereof and communicating with said slot;

g. a slide bar comprising an elongated member of greater length than said slide bar housing and of a transverse cross-sectional configuration corresponding to that of the slot in said slide bar housing, said slide bar having gear teeth along the bottom edge thereof exposed through the opening in the bottom wall of said housing;

grinding wheel dressing tools mounted on and extending upwardly adjacent opposite ends of said slide bar;

. a slide bar operating shaft rotatably mounted within the axially extending bore in said rigid stud and having on the rear end thereof a spur gear in engagement with the gear teeth on the bottom edge of said slide bar; and

j. means for rotating said shaft and the spur gear mounted thereon to reciprocate said slide bar first in one direction and then in the reverse direction, whereby said dressing tools on said slide bar will serve to dress the peripheral face or portions of said face of an abrasive grinding wheel to the precise angle determined by the engagement of the selector pin with the selected notch on the front face of said index disc when said grinding wheel is rotated and is brought into a position where one of the reciprocating dressing tools will engage the periphery thereof.

2. A device as defined in claim l wherein said inner wall defining the circular recess in the rear face of said vertical riser is provided with a second aperture spaced radially from said centrally located aperture in said rear wall and extending through said wall to the front face of said riser, said second aperture being in axial alignment with one of the notches on the front face of said index disc when said index disc is rotated about said fixed stud to select the precise angular setting for said slide bar housing and slide bar, and wherein said selector pin is slidably mounted in said second aperture.

3. A device as defined in claim ll wherein each of the circumferentially spaced notches on the front face of said index disc is defined by inwardly sloping sidewalls, and wherein the outer end of said selector pin is provided with a tapering lug for firm engagement with the inwardly sloping sidewalls which define each of said notches.

d. A device as defined in claim 2 wherein said selector pin is surrounded by two tubular sleeves, the innermost of which iii rigidly secured within said second aperture in said vertical riser and is provided on its outer end with a double spiral cam surface, and wherein the outermost of which is secured to the forward end portion of said selector pin and is provided on its inner end with a double spiral cam surface in operative engagement with the double spiral cam surface on the forward llll end of the innermost tubular sleeve, whereby rotation of said outermost sleeve will cause forward movement of said selector pin due to the cooperative engagement between the double spiral cam surfaces on the respective tubular sleeves.

5. A device as defined in claim 4 wherein said selector pin is hollow throughout the greater portion of its length from its closed inner end toward its outer end, and is provided with a pair of diametrically opposed, axially extending elongated slots formed in the wall surrounding the hollow portion of said selector pin, and wherein a transverse pin of a diameter slightly less than the width of said slots passes through said slots and through said hollow portion of said selector pin with the ends of said transverse pin secured in diametrically opposed openings formed near the outer end of said innermost tubular sleeve and spaced from the closed inner end thereof, engagement between the ends of said slots with said transverse pin limiting the extent of inward and outward movements of said selector pin.

6. A device as defined in claim 5 wherein a coiled compressor spring is positioned within the hollow portion of said selector pin and extends between the closed inner end thereof and said transverse pin and serves to force said selector pin inwardly as the double spiral cam surfaces are moved into engagement by rotation of the outermost of said tubular sleeves.

'7. A device as defined in claim l wherein the forward end of said rigid stud extends forwardly beyond the front face of said riser and is externally threaded, and. wherein a rotatable, internally threaded binding nut engages said externally threaded portion of said rigid stud, rotation of said binding nut in one direction forcing the inner end surface of said binding nut into finn engagement with the front face of said riser to retain the parts in their preselected angular positions and rotation of said binding nut in the reverse direction serving to release said inner end surface thereof for engagement with said front face of said riser to permit movement of said parts to the preselected angular positions.

8. A device as claimed in claim 1, wherein the said slide bar operating shaft extends forwardly beyond the forward end of the rigid stud within which it is rotatably mounted and has secured to said forward end an operating handle movable through approximately from one side of the axis of said slide bar operating shaft to the other to effect rotation of said shaft first in one direction and then in the opposite direction to reciprocate the slide bar and the grinding wheel dressing tools mounted thereon during the wheel dressing operation.

9. A device as claimed in claim d wherein means are provided for adjusting the angular position of said operating handle with respect to the axis of said slide bar operating shaft, whereby said operating handle may be removed to a substantially horizontal position for all angular settings of said index disc and of the parts mounted thereon to permit movement of said operating handle through approximately 180 from side to side of the axis of said slide bar operating shaft regardless of the degree of said angular settings of said parts.

110. A device as claimed in claim 9 wherein a transverse pin extends through said slide bar operating shaft near the forward end thereof, which pin is of a greater length than the diameter of said shaft, and wherein said slide bar operating handle is mounted on and secured to a tubular bushing which surrounds and is slidable along the forward end of said slide bar operating shaft outwardly beyond said transverse pin, the inner end of said tubular bushing being provided with a plurality of radially-extending, diametrically-opposed semicirctilar grooves, any pair of which grooves may be selectively engaged with the extended ends of said pin to determine the angular relation between said slide bar operating shaft and said slide bar operating handle, and means for retaining said engagement during the grinding wheel dressing operation.

lll. A device for dressing the peripheral face or portions of said face of an abrasive grinding wheel to the desired precise iii angle or angles determined by the engagement between a sine button and a gauge block or gauge block combinations, comprising:

a. a base;

b. a vertical riser extending upwardly from said base and having a circular recess in the rear face thereof, the inner vertical wall dening the base of said recess being provided with a centrally located aperture extending through said wall to the front face of said vertical riser;

c. opposed gauge block stops, one at each side of said riser and extending rearwardly beyond the rear face of said riser near the lower portion thereof, with the inner opposed faces of said stops spaced apart a predetermined, fixed distance;

d. a rigid stud secured within said centrally located aperture and having its rear end portion extending through said circular recess and terminating in the plane of the rear face of said riser, said stud having an axially-extending, open-ended bore throughout the length thereof;

e. a disc rotatably mounted in said circular recess on that portion of said rigid stud which extends through said circular recess, said disc having on the rear face thereof a rearwardly-extending sine button located a predetermined radial distance from the axis of said rigid stud equal to approximately one-half the distance between the opposed faces of said gauge block stops;

f. a slide bar housing rigidly secured to the rear face of said rotatable disc to be rotated therewith, said housing being provided with an open-ended slot extending throughout the length thereof, the wall defining the bottom of said slot having an opening therein about midway of the length of said wall and communicating with said slot;

g. a slide bar comprising an elongated member of greater length than said slide bar housing and of a transverse configuration corresponding to that of said slot in said slide bar housing, said slide bar having gear teeth along the bottom edge thereof exposed through the said opening in the bottom wall of said housing;

h. grinding wheel dressing tools mounted on and extending upwardly adjacent opposite ends of said slide bar;

i. a slide bar operating shaft rotatably mounted within the axially-extending bore in said rigid stud and having secured to the rear end of said shaft a spur gear in engagement through the opening in the bottom wall defining the slot in said slide bar housing with the gear teeth on the bottom edge of said slide bar;

j. means for rotating said shaft and the spur gear mounted k. means for rotating said disc about its mounting on said rigid stud to position said slide bar housing and slide bar to the desired angle to dress said peripheral face or portions thereof accordingly, the extent of said rotation being determined by contact between said sine button on said disc and a gauge block or gauge block combination positioned adjacent one of said gauge block stops, the arrangement being such that by determining the sine of the desired angle from a trigonometric chart, multiplying this figure by the predetermined distance between the center of said sine button and the axis of said disc, and then subtracting the resulting figure from the predetermined distance between said sine button and the selected gauge block stop when said slide bar housing is in a truly horizontal position and said sine button is positioned midway between the faces of said opposed gauge block stops, the result of said mathematical calculations determining the effective length of a gauge block combination which should be inserted adjacent the selected gauge block stop to be engaged by said sine button upon rotation of said disc to thus determine the desired angular setting of said slide bar housing and the precise angle to which the peripheral face or portions of said face of a grinding wheel is to be dressed upon operation of said slide bar shaft and slide bar; and

l. means for rigidly securing said disc and slide bar housing in its angular adjusted position preparatory to the dressing of an abrasive grinding wheel. 

1. A device for dressing the peripheral face or portions of said face of an abrasive grinding wheel to the desired precise angle or angles comprising: a. a base; b. a vertical riser extending upwardly From said base and having a circular recess in the rear face thereof, said rear face having thereon a scale of angle designations arranged in preselected angular degree increments and surrounding the wall defining said circular recess, the inner wall defining the base of said recess being provided with a centrally located aperture extending through said wall to the front face of said riser; c. a rigid stud secured within said centrally located aperture and having its rear end portion extending through said circular recess and terminating in the plane of the rear face of said riser, with the front end portion of said stud extending forwardly of the front face of said riser, said stud having an axially extending, open-ended bore throughout the length thereof; d. an index disc rotatably mounted in said circular recess on that portion of said rigid stud which extends through said circular recess, said index disc having on its rear face near the periphery thereof an index mark adapted to be brought into registration with any one of the angle designations of the scale on the rear face of said riser, said index disc having on the front face thereof a series of circumferentially-spaced notches spaced apart at distances corresponding to the angle designations of said scale; e. a selector pin to be engaged within and retractable from one of the series of notches on said index disc, said pin when engaged within one of said series of notches preventing rotation of said index disc on said rigid stud and when retracted from engagement with one of said notches permitting such rotation; f. a slide bar housing rigidly secured to the rear face of said index disc to be rotatable therewith and provided with an openended slot extending axially throughout the length of said housing, the wall defining the bottom of said slot having an opening therein about midway of the length thereof and communicating with said slot; g. a slide bar comprising an elongated member of greater length than said slide bar housing and of a transverse cross-sectional configuration corresponding to that of the slot in said slide bar housing, said slide bar having gear teeth along the bottom edge thereof exposed through the opening in the bottom wall of said housing; h. grinding wheel dressing tools mounted on and extending upwardly adjacent opposite ends of said slide bar; i. a slide bar operating shaft rotatably mounted within the axially extending bore in said rigid stud and having on the rear end thereof a spur gear in engagement with the gear teeth on the bottom edge of said slide bar; and j. means for rotating said shaft and the spur gear mounted thereon to reciprocate said slide bar first in one direction and then in the reverse direction, whereby said dressing tools on said slide bar will serve to dress the peripheral face or portions of said face of an abrasive grinding wheel to the precise angle determined by the engagement of the selector pin with the selected notch on the front face of said index disc when said grinding wheel is rotated and is brought into a position where one of the reciprocating dressing tools will engage the periphery thereof.
 2. A device as defined in claim 1 wherein said inner wall defining the circular recess in the rear face of said vertical riser is provided with a second aperture spaced radially from said centrally located aperture in said rear wall and extending through said wall to the front face of said riser, said second aperture being in axial alignment with one of the notches on the front face of said index disc when said index disc is rotated about said fixed stud to select the precise angular setting for said slide bar housing and slide bar, and wherein said selector pin is slidably mounted in said second aperture.
 3. A device as defined in claim 1 wherein each of the circumferentially spaced notches on the front face of said index disc is defined by inwardly sloping sidewalls, and wherein the outer end of said selector pin is provIded with a tapering lug for firm engagement with the inwardly sloping sidewalls which define each of said notches.
 4. A device as defined in claim 2 wherein said selector pin is surrounded by two tubular sleeves, the innermost of which is rigidly secured within said second aperture in said vertical riser and is provided on its outer end with a double spiral cam surface, and wherein the outermost of which is secured to the forward end portion of said selector pin and is provided on its inner end with a double spiral cam surface in operative engagement with the double spiral cam surface on the forward end of the innermost tubular sleeve, whereby rotation of said outermost sleeve will cause forward movement of said selector pin due to the cooperative engagement between the double spiral cam surfaces on the respective tubular sleeves.
 5. A device as defined in claim 4 wherein said selector pin is hollow throughout the greater portion of its length from its closed inner end toward its outer end, and is provided with a pair of diametrically opposed, axially extending elongated slots formed in the wall surrounding the hollow portion of said selector pin, and wherein a transverse pin of a diameter slightly less than the width of said slots passes through said slots and through said hollow portion of said selector pin with the ends of said transverse pin secured in diametrically opposed openings formed near the outer end of said innermost tubular sleeve and spaced from the closed inner end thereof, engagement between the ends of said slots with said transverse pin limiting the extent of inward and outward movements of said selector pin.
 6. A device as defined in claim 5 wherein a coiled compressor spring is positioned within the hollow portion of said selector pin and extends between the closed inner end thereof and said transverse pin and serves to force said selector pin inwardly as the double spiral cam surfaces are moved into engagement by rotation of the outermost of said tubular sleeves.
 7. A device as defined in claim 1 wherein the forward end of said rigid stud extends forwardly beyond the front face of said riser and is externally threaded, and wherein a rotatable, internally threaded binding nut engages said externally threaded portion of said rigid stud, rotation of said binding nut in one direction forcing the inner end surface of said binding nut into firm engagement with the front face of said riser to retain the parts in their preselected angular positions and rotation of said binding nut in the reverse direction serving to release said inner end surface thereof for engagement with said front face of said riser to permit movement of said parts to the preselected angular positions.
 8. A device as claimed in claim 1, wherein the said slide bar operating shaft extends forwardly beyond the forward end of the rigid stud within which it is rotatably mounted and has secured to said forward end an operating handle movable through approximately 180* from one side of the axis of said slide bar operating shaft to the other to effect rotation of said shaft first in one direction and then in the opposite direction to reciprocate the slide bar and the grinding wheel dressing tools mounted thereon during the wheel dressing operation.
 9. A device as claimed in claim 8 wherein means are provided for adjusting the angular position of said operating handle with respect to the axis of said slide bar operating shaft, whereby said operating handle may be removed to a substantially horizontal position for all angular settings of said index disc and of the parts mounted thereon to permit movement of said operating handle through approximately 180* from side to side of the axis of said slide bar operating shaft regardless of the degree of said angular settings of said parts.
 10. A device as claimed in claim 9 wherein a transverse pin extends through said slide bar operating shaft near the forward end thereof, which pin is of a greater length than the diametEr of said shaft, and wherein said slide bar operating handle is mounted on and secured to a tubular bushing which surrounds and is slidable along the forward end of said slide bar operating shaft outwardly beyond said transverse pin, the inner end of said tubular bushing being provided with a plurality of radially-extending, diametrically-opposed semicircular grooves, any pair of which grooves may be selectively engaged with the extended ends of said pin to determine the angular relation between said slide bar operating shaft and said slide bar operating handle, and means for retaining said engagement during the grinding wheel dressing operation.
 11. A device for dressing the peripheral face or portions of said face of an abrasive grinding wheel to the desired precise angle or angles determined by the engagement between a sine button and a gauge block or gauge block combinations, comprising: a. a base; b. a vertical riser extending upwardly from said base and having a circular recess in the rear face thereof, the inner vertical wall defining the base of said recess being provided with a centrally located aperture extending through said wall to the front face of said vertical riser; c. opposed gauge block stops, one at each side of said riser and extending rearwardly beyond the rear face of said riser near the lower portion thereof, with the inner opposed faces of said stops spaced apart a predetermined, fixed distance; d. a rigid stud secured within said centrally located aperture and having its rear end portion extending through said circular recess and terminating in the plane of the rear face of said riser, said stud having an axially-extending, open-ended bore throughout the length thereof; e. a disc rotatably mounted in said circular recess on that portion of said rigid stud which extends through said circular recess, said disc having on the rear face thereof a rearwardly-extending sine button located a predetermined radial distance from the axis of said rigid stud equal to approximately one-half the distance between the opposed faces of said gauge block stops; f. a slide bar housing rigidly secured to the rear face of said rotatable disc to be rotated therewith, said housing being provided with an open-ended slot extending throughout the length thereof, the wall defining the bottom of said slot having an opening therein about midway of the length of said wall and communicating with said slot; g. a slide bar comprising an elongated member of greater length than said slide bar housing and of a transverse configuration corresponding to that of said slot in said slide bar housing, said slide bar having gear teeth along the bottom edge thereof exposed through the said opening in the bottom wall of said housing; h. grinding wheel dressing tools mounted on and extending upwardly adjacent opposite ends of said slide bar; i. a slide bar operating shaft rotatably mounted within the axially-extending bore in said rigid stud and having secured to the rear end of said shaft a spur gear in engagement through the opening in the bottom wall defining the slot in said slide bar housing with the gear teeth on the bottom edge of said slide bar; j. means for rotating said shaft and the spur gear mounted thereon to reciprocate said slide bar first in one direction and then in the reverse direction, whereby one of said wheel dressing tools on said slide bar serves to dress the peripheral face or portions of said face of an abrasive grinding wheel which is rotated and is brought into a position where said one of said reciprocating tools will engage the peripheral face or portions of said face; k. means for rotating said disc about its mounting on said rigid stud to position said slide bar housing and slide bar to the desired angle to dress said peripheral face or portions thereof accordingly, the extent of said rotation being determined by contact between said sine button on said disc and a gauge block or gauge block combinatiOn positioned adjacent one of said gauge block stops, the arrangement being such that by determining the sine of the desired angle from a trigonometric chart, multiplying this figure by the predetermined distance between the center of said sine button and the axis of said disc, and then subtracting the resulting figure from the predetermined distance between said sine button and the selected gauge block stop when said slide bar housing is in a truly horizontal position and said sine button is positioned midway between the faces of said opposed gauge block stops, the result of said mathematical calculations determining the effective length of a gauge block combination which should be inserted adjacent the selected gauge block stop to be engaged by said sine button upon rotation of said disc to thus determine the desired angular setting of said slide bar housing and the precise angle to which the peripheral face or portions of said face of a grinding wheel is to be dressed upon operation of said slide bar shaft and slide bar; and l. means for rigidly securing said disc and slide bar housing in its angular adjusted position preparatory to the dressing of an abrasive grinding wheel. 